x/m = kP^(1/n), where x = mass of gas adsorbed, m = mass of adsorbent, P = pressure, k and n are constants (n > 1). Logarithmic form: log(x/m) = log k + (1/n) log P. Plot of log(x/m) vs log P: straight line with slope = 1/n and intercept = log k. At low pressure: x/m is proportional to P (1/n approaches 1). At high pressure: x/m approaches constant (1/n approaches 0). Freundlich isotherm fails at very high pressures (doesn't predict saturation properly). Valid only over limited pressure range.